GPS, accuracy and blind spots

NavForge works out where you are from the satellites overhead, not from the mobile network. That is why it keeps navigating when the bars run out — and it is also why there are a few places it goes quiet. This page gives the real numbers, measured from 139 recorded rides, and is honest about the one case where you have to help it along.

Where your position comes from

Your phone has a satellite receiver in it. NavForge asks Android for that receiver directly and takes a fresh position once a second, every second, from the moment you open the app — not only while you are navigating. It does not use the “fused” location that most apps use, which blends in phone masts and Wi-Fi networks to save battery. Raw satellite fixes are slower to warm up and use a little more power, but they are the honest ones, and they do not stop working when the coverage does.

NavForge holds the receiver awake itself, through the ongoing notification you can see in your pull-down shade. Android will not doze it off in your pocket. That is what the notification is for.

None of this needs a signal.

Satellite positioning is a one-way broadcast. Your phone listens; nothing is sent back, and nothing is paid for. Combined with the map and routing already being on the phone, that is the whole reason NavForge carries on out in the scrub. See What works without signal for the full line between the two.

How accurate is it, really

These are not figures from a brochure. They come from every ride log we hold — 139 rides between 13 June and 15 September 2026, 54 and a half hours of riding, 192,043 separate position fixes, all on a phone mounted on a bike in New South Wales and the ACT.

  • Half of all fixes were accurate to 2 metres or better. That is the median.
  • Two thirds were inside 5 metres, and almost all of the rest sat between 5 and 10 metres.
  • 97% were inside 10 metres. 99.9% were inside 20 metres.
  • Only 22 fixes out of 192,043 were worse than 50 metres — and 18 of those 22 happened in the first minute after the app was opened.

For riding, a couple of metres is the difference between the correct lane and the one beside it, and NavForge is comfortably better than that most of the time. Where it gets vaguer — 7 or 8 metres — it is still well inside the width of a road, which is all the app needs to know which road you are on.

The accuracy number is the phone’s own opinion of itself.

Every fix arrives with an accuracy figure attached, and that figure is produced by the phone’s receiver, not measured against a surveyed marker. Android defines it as the radius it is about two-thirds confident you are inside. It is a good guide and it is not a guarantee. We report it honestly rather than pretending we have checked it against ground truth, because we haven’t.

Does it drop out?

Hardly ever, and we can put a number on it. Across those same 54 and a half hours, the gap between one position and the next was one second — the full 1 Hz — for essentially the entire time.

There were 14 occasions where the bike was moving and more than two seconds passed without a new position. Twelve of them turn out to be the app itself stopping and starting — ending navigation, or stopping a recording — and not the satellites at all. That leaves two genuine dropouts in 54 and a half hours of riding: one of 3 seconds and one of 2.2 seconds. A blink each.

So the short answer to “does the GPS have blind spots?” is: on open road, effectively no. The blind spots are all in specific places, and they are worth knowing.

The four places it struggles

  1. The first minute after you open the app

    A satellite receiver that has been off needs to find the satellites again, and with no mobile signal to give it a hint it does this the slow way. This is where almost every poor fix in our data came from — 18 of the 22 readings worse than 50 metres. NavForge covers the gap by showing your last known position straight away, so the first dot you see may be where you were, not where you are. It settles within a minute. Give it that minute before you pull out.

  2. Underground and undercover

    Tunnels, basement car parks, multi-storey carparks. No sky, no satellites, no position. Nothing can fix this — it is physics, not software. What matters is how quickly the app picks you up again on the way out, which is its own section below.

  3. Between tall buildings

    In a city centre, signals bounce off glass and concrete before reaching you, and the receiver can place you on the wrong side of the street. You will see the accuracy figure climb and the dot wander. It corrects itself as soon as you have sky again.

  4. After a long stop

    When you pull up for a coffee and the receiver has been sitting still, the first fixes on the way out are looser than usual. Measured across every stop of more than 30 seconds in our logs: accuracy was typically 2.3 metres before the stop and 5.4 metres on the first fix afterwards. It tightens again within a few seconds of moving.

What you see on screen when the signal goes

NavForge does not pretend about your speed. If five seconds pass with no new position, the speed number blanks to a single — rather than leaving the last reading sitting there looking current. Your blue dot stops where the last good fix put it — the app does not guess your position forward from your last known speed. There is no dead reckoning in NavForge at all.

The speed limit beside it does not blank. It keeps showing the limit for the last road the app knew you were on, which is usually still right — a tunnel rarely changes the limit — but it is worth knowing that the limit number is the one thing on that row which can be stale without saying so.

Five seconds without a position and the speed goes blank rather than lying to you. The limit beside it stays, and so does the turn card’s last instruction.

The same single dash is what you see below about 3 km/h, where a satellite-derived speed stops being meaningful.

The display with no current fix. drawn from code

Coming out of a tunnel

This is the case that needs a word of explanation, because NavForge has to make a judgement call and it used to make the wrong one.

Every position that arrives gets one sanity check: could you really have got there from where you were? A single nonsense reading that puts you 50 km away is thrown out rather than jerking the map across the screen. The check used to be a flat distance — more than 100 metres from the last fix, ignore it — which is fine at one position a second, and wrong the moment you have been out of contact for a while. Come out of a two-kilometre tunnel and your first honest position is two kilometres from your last one, so it looked like nonsense and was discarded, along with every one after it.

NavForge now asks the question the way it was always meant to: not “how far”, but “how fast would that have been”. Two kilometres in two minutes is 60 km/h and perfectly believable, so it is accepted and you carry on. Two kilometres in one second is not, so that is still thrown out. The threshold works out at 360 km/h, which no bike on a public road is going to trouble.

What you actually see in a tunnel.

The speed blanks after five seconds, the blue dot stops at the last position it had, and the turn card holds the last instruction. Voice guidance has nothing new to say, so it goes quiet. Coming back into daylight, everything catches up within a second or two of the first satellite fix — which itself usually takes a few seconds. There is nothing you need to do.

Why offline and satellite-only is the better trade

Riders ask why NavForge does not lean on the mobile network like a phone maps app does. Four reasons, and they are the reasons the app exists.

  • The good roads have no coverage. The places worth riding are exactly the places where a connected navigation app turns into a blank grey screen. NavForge does not change behaviour when the bars disappear, because it was never using them.
  • No data, no roaming, no surprises. Nothing is fetched while you ride — not the map, not the route, not a reroute, not the voice. Crossing a border costs you nothing.
  • Your position stays on your phone. A satellite fix is received, not transmitted. NavForge sends your location off the phone in exactly one situation: when you deliberately join a Group Ride, which exists to share where you are. Otherwise your track is written to your own phone and stays there.
  • A dropped signal cannot strand you. Rerouting is worked out on the phone, so missing a turn 200 km from the nearest tower is handled exactly the same as missing one in town. See When you go off-route.
The one thing a connection genuinely helps with.

A cold receiver finds the satellites faster when the phone can download their orbit data over the network first — that is what “assisted GPS” means, and it is done by Android, not by us. Starting NavForge with a signal, even a bar, shortens that first minute. It makes no difference at all once you are moving.

If the position looks wrong

  1. Give it a minute of open sky

    Most bad positions are a receiver that has not warmed up. Riding out from under a carport or away from a building fixes more of these than anything you can tap.

  2. Check nothing is over the phone

    A tank bag lid, a metallic phone case or a hand across the top of the screen all attenuate the signal. The antenna is usually near the top of the phone.

  3. Check NavForge still has location permission

    Android occasionally withdraws this after an update. If it has gone, NavForge puts a banner across the top of the map reading GPS unavailable — tap to enable in Settings, with a Settings button that takes you straight to the right Android screen. Your first ride walks through granting it.

  4. Stop and restart navigation

    This re-arms the receiver from scratch. It is the blunt instrument, and it is rarely needed — but it costs nothing to try before you report anything.

  5. Tell us, with the ride attached

    Reporting a problem sends the ride log, which contains every position the app was given. That is how the numbers on this page were produced in the first place.

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